from collections import defaultdict
N = int(input())
A = list(map(int, input().split()))
dic = defaultdict(list)
for i, a in enumerate(A):
    dic[a].append(i)
left = 1
right = N - 1
for v in dic.values():
    if len(v) > 2:
        print(0)
        print()
        exit()
    elif len(v) == 2:
        left = max(left, v[0] + 1)
        right = min(right, v[1])
if left <= right:
    print(right - left + 1)
    print(*range(left, right + 1))
else:
    print(0)
    print()